Sustainable chrome tanning system using protein-based product developed from leather waste: wealth from waste

Abstract

Chrome tanning is one of the popular tanning methods followed globally that generates considerable level of chromium pollution in the resulting effluent. The existing conventional chrome tanning system has to be modified to increase the exhaustion level of chromium in the tanning process. In the present investigation, a protein-based product has been developed from raw trimming wastes and applied in chrome tanning process to enhance the exhaustion level of chromium. The experiment conducted using the product at the level of 6% exhibited chromium exhaustion at the level of 93% in the process. FT-IR analysis revealed the presence of peaks for various functional groups, namely carboxylic acids, aldehyde, amide and hydroxyl groups, for the high exhaust chrome tanning. The shrinkage temperature of the experimental leather was found to be more than 100 °C. Results of microscopic studies from SEM–EDX revealed the enhanced adsorption of chromium up to a level of 5.24 weight percent containing chromium with atomic percent 1.27 in the sample of 6% co-polymer. AFM images also show increase in adsorption of chromium with increased amount of co-polymer in the solution. Increased interactions between active sites of collagen complex and chromium resulted into improved exhaustion of chromium as revealed from higher intensities of XRD images. CD spectra revealed that the addition of protein-based product increased the ellipticity of the collagen in the experimental sample as compared to control sample. The crust leather showed improved colour, organoleptic and comparable strength properties of the experimental leather.